196 
LIMN^AD^. 
The spire of the shell is sometimes eroded, and 
because the specimens which Mr, Jeffreys observed 
in this state were a little more ventricose, he has 
described them as a different species. 
The foot is divided transversely very deeply, as in 
Pedipes ; it is very slow in its motion in conse- 
quence of a double action of the foot being necessary 
to effect progression. 
Fam. 5. LIMN-® AD.®. 
Animal with an elongate foot, a more or less conical 
spiral body, a short muzzle, with dilated lips 
and compressed tentacles, with the eyes near 
the inner side of their base: the mantle, which 
covers the body, has a thin edge and is pro- 
tected by a variably shaped pale uniform- 
coloured shell, which is clothed with a hard 
olive periostracum. 
They live in ponds and ditches, often floating on 
the surface of the water, their back downwards, or 
crawling on the mud at the bottom, or on aquatic 
plants, but always coming to the surface to respire. 
These animals were scattered about by the Lin- 
ngean conchologists among the Helices^ the Turbines^ 
the Bullce^ the Nautili^ and the Patellce^ because 
their shells vary considerably in their shape and 
form; they form, however, a most natural group, 
from their having very similar animals. Like water- 
plants, they are distributed very widely, and are to 
be found in almost all parts of the world. 
